Interior surface modifications of molecular sieves with organometallic reagents and the use thereof for the conversion of oxygenates to olefins

ABSTRACT

A method for the post synthesis modification of molecular sieves with organometallic reagents. The method may be used for large pore molecular sieves and small pore molecular sieves, such as SAPO-34. SAPO-34 is a useful catalyst for the conversion of oxygenates, such as methanol, to olefins. Post synthesis organometallic modification improves catalyst performance and increases light olefin selectivity in the conversion of methanol to olefins.

FIELD OF THE INVENTION

[0001] The invention is directed to a method for modifying the interiorsurface of molecular sieves, the modified molecular sieves, and a methodfor converting an oxygenate feedstock to a product, including an olefin.In particular, the invention is directed to modifying asilicoaluminophosphate molecular sieve with an organometallic reagent,the modified silicoaluminophosphate molecular sieve, and a method forconverting an oxygenate feedstock to a product, including an olefin,with the modified silicoaluminophosphate molecular sieve.

BACKGROUND OF THE INVENTION

[0002] Olefins, particularly light olefins, have been traditionallyproduced from petroleum feedstocks by either catalytic or steamcracking. Oxygenates, however, are becoming an alternative feedstock formaking light olefins, particularly ethylene and propylene. Promisingoxygenate feedstocks are alcohols, such as methanol and ethanol,dimethyl ether, methyl ethyl ether, diethyl ether, dimethyl carbonate,and methyl formate. Many of these oxygenates can be produced from avariety of sources including synthesis gas derived from natural gas;petroleum liquids; and carbonaceous materials, including coal. Becauseof the relatively low-cost of these sources, alcohol, alcoholderivatives, and other oxygenates have promise as an economical,non-petroleum source for light olefin production.

[0003] One way of producing olefins is by the catalytic conversion ofmethanol using a silicoaluminophosphate (SAPO) molecular sieve catalyst.For example, U.S. Pat. No. 4,499,327 to Kaiser, discloses making olefinsfrom methanol using a variety of SAPO molecular sieve catalysts. Theprocess can be carried out at a temperature between 300° C. and 500° C.,a pressure between 0.1 atmosphere to 100 atmospheres, and a weighthourly space velocity (WHSV) of between 0.1 and 40 hr⁻¹.

[0004] Inui (J. Chemical Society Chem. Commun. p.205, 1990) has shownthat the selectivity to ethylene can be increased when methanol iscontacted with a nickel-substituted SAPO-34 rather than an unsubstitutedSAPO-34. In this case, nickel substitution occurred into the SAPO-34framework.

[0005] In contrast to the work of Kaiser and Inui, metal incorporationmay also take place post-synthesis, that is, following the synthesis ofthe molecular sieve framework. For example, U.S. Pat. No. 5,962,762 toSun et al. teaches a process for converting methanol to light olefinsusing a metal-incorporated SAPO catalyst. An aqueous metal solution,preferably a nickel or cobalt containing solution, is adsorbed onto theSAPO molecular sieve by allowing the solution to remain in contact withthe SAPO overnight at ambient conditions. The treated molecular sieve isthen separated from the solution and dried. U.S. Pat. Nos. 5,625,104 and5,849,968 to Beck at al. teach a process of incorporating alkali earthand alkaline earth metals into a zeolitic catalyst by pretreating thezeolite with an organosilicon or poly-oxo silicon compound followed bythe treatment of a metal solution. U.S. Pat. No. 4,692,424 to Le Van Maoteaches a process for the dry incorporation of manganese ions on theexternal reactive sites of ZSM catalysts by adding a minimum amount ofan aqueous manganese solution to form a malleable paste and extrudingthe paste under pressure.

[0006] Post-synthesis metal incorporation of zeolite catalysts is usedfor other processes as well. U.S. Pat. No. 6,084,142 to Yao et al.teaches treating a zeolite catalyst with a zinc component in an aqueoussolution followed by steam treatment for the conversion of hydrocarbonsto lower olefins. There is no teaching of conversion of methanol toolefins.

[0007] Yamamoto et al. (Microporous and Mesoporous Materials 44-45,Organic Functionalization of Mesoporous Molecular Sieves with GrignardReagents, p.459-464, 2001) teach post-synthesis organicfunctionalization of MCM-41 in a two step procedure. MCM-41 is firstmodified by alcohols, which leads to the esterification of surfacesilanol groups (converting Si—OH to Si—OR) and then allowed to reactwith a Grignard reagent R′MgX which converts Si—OR to Si—R′. The twostep procedure must be followed since Si—OH spoils Grignard reagentR′MgX to form Si—O—MgX and R′—H. There is no teaching of conversion ofmethanol to olefins.

[0008] PCT Application WO 97/26989 teaches adding a transition metalhydrogenation component in a non-aqueous solvent to a non-zeoliticmolecular sieve after synthesis for hydrocracking and catalyticdewaxing. The hydrogenation component is in the form of a sulfide,halide, oxide, carboxylate, and the like. There is no teaching ofconversion of methanol to olefins.

[0009] In spite of the prior efforts to modify molecular sieves, theneed to modify the surface, in particular the interior surface, of smallpore molecular sieves such as silicoaluminophosphates (SAPO) remains.Consequently, there is still a need to find an improved molecular sieveor molecular sieve catalyst that exhibits high ethylene and/or propyleneselectivity in the conversion of methanol to light olefins.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 shows the evolution of methane during dimethyl zinctreatment of SAPO-34 in heptane.

[0011]FIG. 2 shows the evolution of methane during methylmagnesiumbromide treatment of SAPO-34 in a mixture of toluene and tetrahydrofuran(THF).

[0012]FIG. 3 shows MAS ¹H NMR of zinc modified SAPO-34 via differentzinc modification methods.

[0013]FIG. 4 shows conversion and selectivity data for fresh andregenerated SAPO-34 modified with dimethyl zinc.

SUMMARY OF THE INVENTION

[0014] The invention provides a method for making an organometallictreated molecular sieve comprising:

[0015] a) providing a molecular sieve having at least one hydroxylgroup;

[0016] b) contacting said molecular sieve with a solution comprising anorganometallic compound and a non-proton donating solvent, wherein saidorganometallic compound comprises at least one metal bound to at leastone alkyl group; and

[0017] c) separating the organometallic treated molecular sieve from thesolution.

[0018] The invention relates to an organometallic treated molecularsieve, particularly a silicoaluminophosphate molecular sieve, obtainableby the method of the present invention. The organometallic compound isincorporated into, onto, or within the molecular sieve by chemicalreactions to modify both the internal and external surfaces, preferablythe internal surface, of the molecular sieve.

[0019] The invention further relates to a catalyst comprising anorganometallic treated molecular sieve, particularly asilicoaluminophosphate molecular sieve, according to the invention.

[0020] The invention also relates to a method of making an olefinicproduct, wherein the catalyst comprising an organometallic treatedmolecular sieve, particularly a silicoaluminophosphate molecular sieve,is contacted with a feedstock comprising at least one organic compoundthat contains at least one oxygen atom (oxygenate) under conditionssuitable to convert the oxygenate into olefins.

[0021] Organometallic reagents comprising at least one metal bound to atleast one alkyl group, such as methyl lithium, butyl lithium, dimethylzinc, diethyl zinc, ethylmagnesium bromide, methylmagnesium bromide,trimethyl gallium, thiethyl gallium, tetraethyl germanium, andtetramethyl germanium can be used in the method of the presentinvention.

[0022] The method of the present invention can be used for large poremolecular sieves, but are especially important for the modification ofsmall pore molecular sieves such as SAPO-34. SAPO-34, an eight-ringsilicoaluminophosphate catalyst, is a preferred catalyst for theconversion of oxygenates, especially methanol, to olefins.

[0023] We have discovered a post-synthesis modification method usingorganometallic compounds as the modifying reagents. With thismodification, metal species are incorporated into, onto, or within themolecular sieves through chemical reactions with the hydroxyl groups inthe molecular sieves. The proper size of the reagent and the nature ofthe chemical reactions determine the location, preferably on theinterior surface of the molecular sieve, of the metal introduced.Compared to conventional post-synthesis methods, the method of thepresent invention requires mild conditions and offers control ofreaction mechanisms such as the loading of the metal, the site anddegree of reaction, and the location of the metal, therefore offering acontrollable approach to improve catalyst performance.

[0024] Post-synthesis organometallic modification, according to themethod of the present invention, provides a vehicle to improve catalystperformance for conversion of methanol to olefins by fine-tuning acidityand pore volume of the molecular sieve. As a result, both acidity andpore volume are modified as reflected in changes in catalyst structureand performance. For example, we have found that treating SAPO-34 withdimethyl zinc increases light olefin selectivity, with increasingethylene to propylene ratio as zinc loading increases.

[0025] We have discovered a method to modify the interior surfaces ofmolecular sieves employing organometallic reagents in non-protondonating solvents. Increases in light olefin selectivity, especiallyethylene selectivity, can be achieved, using the method of the presentinvention. For example, dimethyl zinc, Zn(CH₃)₂, can easily get into thecage of SAPO-34 and react at the interior acid sites, resulting ininterior surface modification of the molecular sieve. The yield ofethylene from methanol to olefin (MTO) conversion with SAPO-34 can beincreased when SAPO-34 is modified with dimethyl zinc.

DETAILED DESCRIPTION OF THE INVENTION

[0026] This invention relates to a method for modifying molecularsieves?, particularly silicoaluminophosphate molecular sieves, with anorganometallic compound. When these organometallic modified molecularsieves are used in the catalytic conversion of methanol to lightolefins, they exhibit higher selectivities to ethylene and/or propylenethan the corresponding unmodified molecular sieve.

[0027] According to the present invention, molecular sieves are treatedwith organometallic reagents after the molecular sieve structures areformed. Incorporating the metal after the molecular sieve has beenprepared has several advantages over that of metal incorporation duringmolecular sieve synthesis. The physical characteristics of the molecularsieve, such as particle and pore size, can be varied prior to metalincorporation. As a result, post-synthesis techniques provide widerpossibilities in molecular sieve preparation and screening. For example,a particular metal can be tested over a wide variety of molecularsieves, or a particular molecular sieve can be tested over a wide rangeof metals. Also, the molecular sieve structures obtained by the variousmethods can differ significantly, which is reflected in significantdifferences in catalytic behaviors.

[0028] Molecular sieves that may be used in accordance with the presentinvention are silicoaluminophosphates (SAPOs) and aluminosilicateshaving an average pore opening of at least 3 Angstroms. Suitablemolecular sieves include, but are not limited to the structural types ofAEI, AFT, APC, ATN, ATT, ATV, AWW, BIK, CAS, CHA, CHI, DAC, DDR, EDI,ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU, PHI, RHO, ROG, and THO andsubstituted examples of these structural types, as described in Ch.Baerlocher, W. M. Meier, and D. H. Olson, Atlas of Zeolite FrameworkTypes, fifth edition (Elsevier, 2001), incorporated herein by reference.Structural types of medium pore molecular sieves useful in the presentinvention include, but are not limited to, MFI, MEL, MTW, EUO, MTT, HEU,FER, AFO, AEL, TON, and substituted examples of these structural types,as described in the Atlas of Zeolite Framework Types, previouslyincorporated herein by reference. Aluminosilicates that may be used inaccordance with the present invention include, but are not limited to,ZSM-34, chabazite and erionite. SAPO molecular sieves that may be usedin accordance with the invention include, but are not limited to,SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31,SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44,SAPO-47, SAPO-56, and mixtures thereof. Preferred are SAPO-18, SAPO-34,SAPO-35, SAPO-44, SAPO-47 and SAPO-56, particularly SAPO-34,intergrowths of SAPO-34 and SAPO-18, and mixtures thereof. As usedherein, the term mixture is synonymous with combination and isconsidered a composition of matter having two or more components invarying proportions, regardless of their physical state.

[0029] Silicoaluminophosphate molecular sieves (SAPOs) comprise athree-dimensional microporous crystal framework structure of (SiO₂),(AlO₂) and (PO₂) comer sharing tetrahedral units. The way Si isincorporated into the structure can be determined by Si MAS NMR. (SeeBlackwell and Patton, J. Phys. Chem., 92, 3965 (1988)) The desired SAPOmolecular sieves will exhibit one or more peaks in the ²⁹Si MAS NMR,with a chemical shift δ(Si) in the range of −88 to −96 ppm and with acombined peak area in that range of at least 20% of the total peak areaof all peaks with a chemical shift δ(Si) in the range of −88 ppm to −115ppm, where the δ(Si) chemical shifts refer to external tetramethylsilane(TMS).

[0030] SAPO molecular sieves are generally classified as beingmicroporous materials having 8, 10, or 12 membered ring structures.These ring structures can have an average pore size ranging from about3-15 Angstroms. Preferred for MTO conversion are the small pore SAPOmolecular sieves having an average pore opening of at most about 6Angstroms, preferably an average pore opening of at most about 5.5Angstroms, and more preferably at most about 4.2 Angstroms. The averagepore opening is at least about 3 Angstroms, preferably at least about3.5 Angstroms, and more preferably at least about 3.8 Angstroms. Thesepore openings are typical of molecular sieves having 8 membered rings.

[0031] SAPO molecular sieves comprise a molecular framework ofcomer-sharing (SiO₂), (AlO₂) and (PO₂) tetrahedral units. Molecularsieves with this type of framework such as SAPO-34 are effective inconverting feedstocks containing oxygenates into olefin products.

[0032] The (PO₂) tetrahedral units within the framework structure of themolecular sieve of this invention can be provided by a variety ofcompositions. Examples of these phosphorus-containing compositionsinclude phosphoric acid, organic phosphates such as triethyl phosphate,and aluminophosphates. The phosphorous-containing compositions are mixedwith reactive silicon and aluminum-containing compositions under theappropriate conditions to form the molecular sieve.

[0033] The (AlO₂) tetrahedral units within the framework structure canbe provided by a variety of compositions. Examples of thesealuminum-containing compositions include aluminum alkoxides such asaluminum isopropoxide, aluminum phosphates, aluminum hydroxide, sodiumaluminate, and pseudoboehmite. The aluminum-containing compositions aremixed with reactive silicon and phosphorus-containing compositions underthe appropriate conditions to form the molecular sieve.

[0034] The (SiO₂) tetrahedral units within the framework structure canbe provided by a variety of compositions. Examples of thesesilicon-containing compositions include silica sols and siliconalkoxides such as tetraethyl orthosilicate.

[0035] In order to prepare a silicoaluminophosphate molecular sieve, thesilicon-containing compositions are mixed with reactive aluminum andphosphorus-containing compositions under the appropriate conditions toform the molecular sieve.

[0036] The silicoaluminophosphates may also contain one or moretemplates. Templates are structure directing or affecting agents, andtypically contain nitrogen, phosphorus, oxygen, carbon, hydrogen or acombination thereof, and can also contain at least one alkyl or arylgroup, with 1 to 8 carbons being present in the alkyl or aryl group.Mixtures of two or more templates can produce mixtures of differentsieves or predominantly one sieve where one template is more stronglystructure-directing than another.

[0037] Representative templates include tetraethyl ammonium salts,cyclopentylamine, aminomethyl cyclohexane, piperidine, diethylamine,triethylamine, cyclohexylamine, tri-ethyl hydroxyethylamine, morpholine,dipropylamine (DPA), pyridine, isopropylamine and combinations thereof.Preferred templates are diethylamine; triethylamine, cyclohexylamine,piperidine, pyridine, isopropylamine, tetraethyl ammonium salts,dipropylamine, and mixtures thereof. The tetraethyl ammonium saltsinclude tetraethyl ammonium hydroxide (TEAOH), tetraethyl ammoniumphosphate, tetraethyl ammonium fluoride, tetraethyl ammonium bromide,tetraethyl ammonium chloride, tetraethyl ammonium acetate. Preferredtetraethyl ammonium salts are tetraethyl ammonium hydroxide andtetraethyl ammonium phosphate. Particularly preferred templates aretriethylamine (TEA) and tetraethyl ammonium hydroxide (TEAOH).

[0038] The SAPO molecular sieves are synthesized by hydrothermalcrystallization methods generally known in the art. See, for example,U.S. Pat. Nos. 4,440,871; 4,861,743; 5,096,684; and 5,126,308, themethods of making of which are fully incorporated herein by reference. Areaction mixture is formed by mixing together reactive silicon, aluminumand phosphorus components, along with at least one template. Generallythe mixture is sealed and heated, preferably under autogenous pressure,to a temperature of at least 100° C., preferably from 100-250° C., untila crystalline product is formed. Formation of the crystalline productcan take anywhere from around 2 hours to as much as 2 weeks. In somecases, stirring, tumbling or seeding with crystalline material willfacilitate the formation of the product.

[0039] Typically, the molecular sieve product is formed in solution. Itcan be recovered by standard means, such as by centrifugation orfiltration. The product can also be washed, recovered by the same means,and dried. As a result of the crystallization process, the recoveredsieve contains within its pores at least a portion of the template usedin making the initial reaction mixture.

[0040] According to the method of the present invention, the molecularsieve may be calcined prior to contacting with the organometalliccompound. The molecular sieve may be calcined to remove at least about90%, preferably at least about 95%, and more preferably at least about99% of the template. Typically, the molecular sieve is calcined at atemperature of at least about 300° C., preferably at least about 450°C., more preferably at least about 550° C. and at a temperature of atmost about 800° C., preferably at most about 750° C., and morepreferably at most about 700° C. The molecular sieve is calcined for aperiod of time of at least about 1 hour, preferably at least about 2hours, more preferably at least about 3 hours and for a period of timeof at most about 24 hours, preferably at most about 12 hours, and morepreferably at most about 10 hours.

[0041] The calcined molecular sieves are then treated with a solutioncontaining an organometallic compound and a non-proton donating solvent.No acid treatment or steam treatment of the molecular sieve is requiredby the method of the present invention.

[0042] The organometallic compound is defined as a compound having atleast one metal bound to at least one alkyl group. The alkyl group islinear and may have up to at most about twenty (20) carbon atoms,preferably at most about twelve (12) carbon atoms, and more preferablyat most about six (6) carbon atoms.

[0043] Metals useful according to the present invention are selectedfrom the group consisting of Group 1 to Group 14, and mixtures thereof.See The Chemistry of the Elements, Second Edition, 1998. Suitable metalsinclude, but are not limited to, lithium, gallium, germanium, magnesium,zinc, and mixtures thereof.

[0044] Suitable organometallic compounds include, but are not limitedto, methyl lithium, butyl lithium, dimethyl zinc, diethyl zinc,ethylmagnesium bromide, methylmagnesium bromide, trimethyl gallium,triethyl gallium, tetraethyl germanium, and tetramethyl germanium andmixtures thereof. Dimethyl zinc is the preferred organometalliccompound.

[0045] The concentration of organometallic compound in the solution istypically at least about 0.001 M, preferably at least about 0.005 M, andmore preferably at least about 0.01 M. The concentration oforganometallic compound in the solution is typically at most about 10.0M, preferably at most about 5.0 M, and more preferably at most about 3.0M.

[0046] Suitable non-proton donating solvents (anhydrous grade) include,but are not limited to, linear or branched alkanes or alkenes having acarbon number between five (5) and twenty (20), such as heptane;halogen-substituted alkanes having more than one (1) carbon, where thehalogen can be fluorine or chlorine; ethers; ketones; sulfoxides;heterocyclic compounds, such as tetrahydrofuran, substituted pyridine orunsubstituted pyridine; aromatic compounds, such as benzene, toluene, orxylenes; and mixtures thereof.

[0047] The organometallic compound containing solution is contacted themolecular sieve, with or without stirring, under autogenous pressure ina reaction vessel. The reaction mixture may or may not be heated and istypically at a temperature of at least about −40° C., preferably atleast about −25° C., more preferably at least about. 0° C. and at atemperature of at most about 200° C., preferably at most about 150° C.,and more preferably at most about 100° C.

[0048] The organometallic compound is contacted with the molecular sievefor a sufficient period of time depending upon the process temperature,the pressure, the type of organometallic compound solution used, theconcentration of the organometallic compound in solution, and the typeof molecular sieve used. Generally, the reaction is allowed to takeplace for several hours. The reaction takes place for a time of at leastabout 1 hour, preferably at least about 2 hours, more preferably atleast about 3 hours and for a time of at most 48 hours, preferably atmost about 24 hours, and more preferably at most about 20 hours. It isto be understood that one of ordinary skill in the art will know how tovary the time of contacting depending upon each of these parameters.

[0049] At this stage, one obtains what may be called an organometallictreated molecular sieve which is then separated from the non-protondonating solvent. The separated molecular sieve is then washed with oneor more organic solvents to remove traces of unreacted or loosely boundorganometallic compound. Suitable organic solvents include, but notlimited to, methanol, ethanol, 2-propanol, diethyl ether, acetone,hexane, heptane, tetrahydrofuran, and toluene. The washed molecularsieve is dried, for example at 110° C. overnight.

[0050] The amount of metal disposed into, onto, or within the pores ofthe organometallic modified molecular sieve is such that the molecularsieve comprises at least about 0.05 percent by weight metal, preferablyat least about 0.5 percent by weight metal, more preferably at leastabout 1.0 percent by weight metal and at most about 20 percent by weightmetal, preferably at most about 10 percent by weight metal, and morepreferably at most about 8 percent by weight metal.

[0051] The organometallic treated molecular sieve can be furthercontacted with a solution of the same or different organometalliccompound according to the method of the present invention. Multiplecycles of contacting the organometallic solution with the molecularsieve can be carried out, if required, to achieve the desired degree ofmetal loading.

[0052] After the organometallic treatment, the resultant metal speciesis disposed into, onto, or within the molecular sieves. The metalspecies is introduced through chemical reactions with the hydroxylgroups of the molecular sieve, wherein the metal species is disposedwithin the pores, on the internal surfaces of the molecular sieve,and/or on the external surfaces of the molecular sieve. Under theconditions used according to the method of the present invention, thealkyl group of the organometallic compound reacts with the hydroxylgroups forming an alkane, such as methane or ethane, and the metalspecies is attached to the sites of the reactive hydroxyl groups, eitherwithin the pores, at the internal and/or external surfaces of themolecular sieve.

[0053] After the organometallic treated molecular sieve is washed anddried, the molecular sieve may be calcined or partially calcined.Typically, the molecular sieve of the invention is calcined, with orwithout oxygen, prior to use, for example, in a conversion reactor. Theorganometallic treated molecular sieve is calcined at a temperature ofat least about 300° C., preferably at least about 450° C., morepreferably at least about 550° C. and at a temperature of at most about800° C., preferably at most about 750° C., and more preferably at mostabout 700° C.

[0054] The molecular sieve is calcined for a period of time of at leastabout 1 hour, preferably at least about 2 hours, more preferably atleast about 3 hours and for a period of time of at most about 24 hours,preferably at most about 12 hours and more preferably at most about 10hours. One thus obtains a calcined organometallic treated molecularsieve.

[0055] The organometallic treated molecular sieves of the presentinvention are useful as catalysts in the conversion of feedstockscontaining at least one organic compound which contains at least oneoxygen atom (hereinafter referred to as an oxygenate) into lightolefins. For this purpose, the silicoaluminophosphates may be used incombination or in admixture with other components.

[0056] Another embodiment of this invention is the composition of theorganometallic modified molecular sieves, particularly organometallicmodified SAPO-34. For example, when dimethyl zinc is used to modifySAPO-34, a new zinc-containing molecular sieve is obtained. This newmaterial has a signature peak that appears around δ=1.0 ppm in the MAS¹H NMR.

[0057] The microporosity of the organometallic modified molecular sievecan be measured by its methanol uptake capacity. The organometallicmodified molecular sieves have reduced methanol uptake capacity ascompared to unmodified molecular sieves, reflecting decreased porevolume. The decreased pore volume is a result of interior surfacemodification by the organometallic reagents.

[0058] An aluminophosphate (ALPO) molecular sieve may be used alone orin combination with the silicoaluminophosphate molecular sieves of thepresent invention. Aluminophosphate molecular sieves are crystallinemicroporous oxides which can have an AlPO₄ framework. They can haveadditional elements within the framework, typically have uniform poredimensions ranging from about 3 angstroms to about 10 angstroms, and arecapable of making size selective separations of molecular species. Morethan two dozen structure types have been reported, including zeolitetopological analogues. A more detailed description of the background andsynthesis of aluminophosphates is found in U.S. Pat. No. 4,310,440,which is incorporated herein by reference in its entirety. PreferredALPOs are ALPO-5, ALPO-11, ALPO-18, ALPO-31, ALPO-34, ALPO-36, ALPO-37,and ALPO-46.

[0059] The ALPOs can also include a metal substituent in its framework.Preferably, the metal is selected from the group consisting ofmagnesium, manganese, zinc, cobalt, and mixtures thereof. Thesematerials preferably exhibit adsorption, ion-exchange and/or catalyticproperties similar to aluminosilicate, aluminophosphate and silicaaluminophosphate molecular sieve compositions. Members of this class andtheir preparation are described in U.S. Pat. No. 4,567,029, incorporatedherein by reference in its entirety.

[0060] The metal containing ALPOs have a three-dimensional microporouscrystal framework structure of MO₂, AlO₂ and PO₂ tetrahedral units.These as manufactured structures (which contain template prior tocalcination) can be represented by empirical chemical composition, on ananhydrous basis, as:

mR: (M_(x)Al_(y)P_(z))O₂

[0061] wherein R represents at least one organic templating agentpresent in the intracrystalline pore system; m represents the moles of Rpresent per mole of (M_(x)Al_(y)P_(z))O₂ and has a value of from zero to0.3, the maximum value in each case depending upon the moleculardimensions of the templating agent and the available void volume of thepore system of the particular metal aluminophosphate involved, x, y, andz represent the mole fractions of the metal M, (i.e. magnesium,manganese, zinc and cobalt), aluminum and phosphorus, respectively,present as tetrahedral oxides

[0062] The metal containing ALPOs are sometimes referred to by theacronym as MeAPO. Also in those cases where the metal Me in thecomposition is magnesium, the acronym MAPO is applied to thecomposition. Similarly ZAPO, MnAPO and CoAPO are applied to thecompositions which contain zinc, manganese and cobalt respectively. Toidentify the various structural species which make up each of thesubgeneric classes MAPO, ZAPO, CoAPO and MnAPO, each species is assigneda number and is identified, for example, as ZAPO-5, MAPO-11, CoAPO-34and so forth.

[0063] The organometallic treated SAPO molecular sieves of the presentinvention can also be admixed (i.e. blended, formulated) with othermaterials. Once prepared, the resulting composition is typicallyreferred to as a SAPO catalyst, with the catalyst comprising the SAPOmolecular sieve. Materials which can be blended with the molecular sievecan be various inert or catalytically active materials, or variousbinder materials. These materials include compositions such as kaolinand other clays, various forms of rare earth metals, metal oxides, othernon-zeolite catalyst components, zeolite catalyst components, alumina oralumina sol, aluminum chlorhydrol, titania, zirconia, magnesia, thoria,beryllia, quartz, silica or silica or silica sol, and mixtures thereof.Preferably an alumina binder such as aluminum chlorhydrol, and/or one ormore clays, such as kaolin, is used in combination with the molecularsieve of the invention. These components are also effective in reducing,inter alia, overall catalyst cost, acting as a thermal sink to assist inheat shielding the catalyst during regeneration, densifying the catalystand increasing catalyst strength.

[0064] Preferably an alumina binder such as aluminum chlorhydrol, and/orone or more clays, such as kaolin, is used in combination with themolecular sieve of the invention. If the molecular sieve is in the dryfrom, a fluid, such as water, is added to form a slurry. More often,however, the catalyst is prepared following the preparation of themolecular sieve which is maintained as a slurry from the precedingcrystallization step. The other components are then added to theslurried molecular sieve as either dry solids and/or as slurries. Thisfinal slurry having a specific solid content and particle size is mixeduntil a relatively uniform distribution of all components is obtained.The uniformly mixed slurry is then spray dried or extruded to form thecatalyst.

[0065] Additional molecular sieve materials can be included as a part ofthe SAPO catalyst composition or they can be used as separate molecularsieve catalysts alone or in admixture with the SAPO catalyst if desired.Structural types of small pore molecular sieves that are suitable foruse in this invention include AEI, AFT, APC, ATN, ATT, ATV, AWW, BIK,CAS, CHA, CHI, DAC, DDR, EDI, ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU,PHI, RHO, ROG, THO, and substituted forms thereof. Structural types ofmedium pore molecular sieves that are suitable for use in this inventioninclude LEV, MFI, MEL, MTW, EUO, MTT, HEU, FER, AFO, AEL, TON, andsubstituted forms thereof. These small and medium pore molecular sievesare described in greater detail in the Atlas of Zeolite Framework Types,which is previously incorporated herein by reference. Preferredmolecular sieves which can be used alone or combined with asilicoaluminophosphate catalyst include ZSM-5, ZSM-34, erionite, levyneand chabazite.

[0066] After formulation, the catalyst composition of the inventiontypically comprises at least about 1%, preferably at least about 5%, andmore preferably at least about 10%, by weight of molecular sieve. Thecatalyst composition typically comprises at most about 99%, preferablyat most about 90%, and more preferably at most about 80%, by weight ofmolecular sieve. The catalyst particles generally have a size of atleast about 20μ, preferably at least about 30μ, and more preferably atleast about 50μ. The catalyst particles generally have a size of at mostabout 3,000μ, preferably at most about 200μ, and more preferably at mostabout 150μ.

[0067] The catalyst particles can be subjected to a variety oftreatments to achieve the desired physical and chemical characteristics.Such treatments include, but are not necessarily limited to hydrothermaltreatment, calcination, acid treatment, base treatment, milling, ballmilling, grinding, spray drying, and combinations thereof.

[0068] The catalyst particles containing an organometallic treatedmolecular sieve according to the present invention are useful ascatalysts for the conversion of hydrocarbons, in particular for thecatalytic conversion of feedstocks containing at least one organiccompound containing at least one oxygen atom (oxygenate) to lightolefins. Accordingly, a third aspect of the invention relates to amethod of making an olefin product, wherein the catalyst of theinvention is contacted with a feedstock comprising at least oneoxygenate under conditions suitable to convert the oxygenate intoolefins.

[0069] In this aspect of the invention, a feedstock containing at leastone oxygenate, and optionally a diluent or a hydrocarbon addedseparately or mixed with the oxygenate, is contacted with a catalystcontaining a SAPO molecular sieve in a reaction zone or volume. Thevolume in which such contact takes place is herein termed the reactor,which may be a part of a reactor apparatus or reaction system. Anotherpart of the reaction system may be a regenerator, which comprises avolume wherein carbonaceous deposits (or coke) on the catalyst resultingfrom the olefin conversion reaction are removed by contacting thecatalyst with regeneration medium.

[0070] The oxygenate feedstock of this invention comprises at least oneorganic compound which contains at least one oxygen atom (oxygenate),such as aliphatic alcohols, ethers, carbonyl compounds (aldehydes,ketones, carboxylic acids, carbonates, esters and the like). When theoxygenate is an alcohol, the alcohol can include an aliphatic moietyhaving from 1 to 10 carbon atoms, more preferably from 1 to 4 carbonatoms. Representative alcohols include but are not necessarily limitedto lower straight and branched chain aliphatic alcohols and theirunsaturated counterparts. Examples of suitable oxygenate compoundsinclude, but are not limited to: methanol; ethanol; n-propanol;isopropanol; C₄-C₂₀ alcohols; methyl ethyl ether; dimethyl ether;diethyl ether; di-isopropyl ether; formaldehyde; dimethyl carbonate;dimethyl ketone; acetic acid; and mixtures thereof Preferred oxygenatecompounds are methanol, dimethyl ether, or a mixture thereof.

[0071] The method of making the preferred olefin product in thisinvention can include the additional step of making these compositionsfrom hydrocarbons such as oil, coal, tar sand, shale, biomass andnatural gas. Methods for making the compositions are known in the art.These methods include fermentation to alcohol or ether, making synthesisgas, then converting the synthesis gas to alcohol or ether. Synthesisgas can be produced by known processes such as steam reforming,autothermal reforming and partial oxidization.

[0072] One or more inert diluents may be present in the feedstock, forexample, in an amount of from 1 to 99 molar percent, based on the totalnumber of moles of all feed and diluent components fed to the reactionzone (or catalyst). As defined herein, diluents are compositions whichare essentially non-reactive across a molecular sieve catalyst, andprimarily function to make the oxygenates in the feedstock lessconcentrated. Typical diluents include, but are not necessarily limitedto helium, argon, nitrogen, carbon monoxide, carbon dioxide, water,essentially non-reactive paraffins (especially the alkanes such asmethane, ethane, and propane), essentially non-reactive alkylenes,essentially non-reactive aromatic compounds, and mixtures thereof. Thepreferred diluents are water and nitrogen. Water can be injected ineither liquid or vapor form.

[0073] Hydrocarbons can also be included as part of the feedstock, i.e.,as co-feed. As defined herein, hydrocarbons included with the feedstockare hydrocarbon compositions which are converted to another chemicalarrangement when contacted with molecular sieve catalyst. Thesehydrocarbons can include olefins, reactive paraffins, reactivealkylaromatics, reactive aromatics or mixtures thereof. Preferredhydrocarbon co-feeds include, propylene, butylene, pentylene, C₄ ⁺hydrocarbon mixtures, C₅ ⁺ hydrocarbon mixtures, and mixtures thereof.More preferred as co-feeds are a C₄ ⁺ hydrocarbon mixtures, with themost preferred being C₄ ⁺hydrocarbon mixtures which are obtained fromseparation and recycle of reactor product.

[0074] In the process of this invention, coked catalyst can beregenerated by contacting the coked catalyst with a regeneration mediumto remove all or part of the coke deposits. This regeneration can occurperiodically within the reactor by ceasing the flow of feed to thereactor, introducing a regeneration medium, ceasing flow of theregeneration medium, and then reintroducing the feed to the fully orpartially regenerated catalyst. Regeneration may also occur periodicallyor continuously outside the reactor by removing a portion of thedeactivated catalyst to a separate regenerator, regenerating the cokedcatalyst in the regenerator, and subsequently reintroducing theregenerated catalyst to the reactor. Regeneration can occur at times andconditions appropriate to maintain a desired level of coke on the entirecatalyst within the reactor.

[0075] Catalyst that has been contacted with feed in a reactor isdefined herein as feedstock exposed. Feedstock exposed catalyst willprovide olefin conversion reaction products having substantially lowerpropane and coke content than a catalyst which is fresh and regenerated.A catalyst will typically provide lower amounts of propane as it isexposed to more feed, either through increasing time at a given feedrate or increasing feed rate over a given time.

[0076] At any given instant in time, some of the catalyst in the reactorwill be fresh, some regenerated, and some coked or partially coked as aresult of having not yet been regenerated. Therefore, various portionsof the catalyst in the reactor will have been feedstock exposed fordifferent periods of time. Since the rate at which feed flows to thereactor can vary, the amount of feed to which various portions of thecatalyst can also vary. To account for this variation, the averagecatalyst feedstock exposure index (ACFE index) is used to quantitativelydefine the extent to which the entire catalyst in the reactor has beenfeedstock exposed.

[0077] As used herein, ACFE index is the total weight of feed divided bythe total weight of molecular sieve (i.e., excluding binder, inerts,etc., of the catalyst composition) sent to the reactor. The measurementshould be made over an equivalent time interval, and the time intervalshould be long enough to smooth out fluctuations in catalyst orfeedstock rates according to the reactor and regeneration process stepselected to allow the system to be viewed as essentially continuous. Inthe case of reactor systems with periodic regenerations, this can rangefrom hours up to days or longer. In the case of reactor systems withsubstantially constant regeneration, minutes or hours may be sufficient.

[0078] Flow rate of catalyst can be measured in a variety of ways. Inthe design of the equipment used to carry the catalyst between thereactor and regenerator, the catalyst flow rate can be determined giventhe coke production rate in the reactor, the average coke level oncatalyst leaving the reactor, and the average coke level on catalystleaving the regenerator. In an operating unit with continuous catalystflow, a variety of measurement techniques can be used. Many suchtechniques are described, for example, by Michel Louge, “ExperimentalTechniques”, Circulating Fluidized Beds, Grace, Avidan, & Knowlton,eds., Blackie, 1997 (336-337), the descriptions of which are expresslyincorporated herein by reference.

[0079] In this invention, only the molecular sieve in the catalyst sentto the reactor may be used in the determination of ACFE index. Thecatalyst sent to the reactor, however, can be either fresh orregenerated or a combination of both. Molecular sieve which may berecirculated to and from the reactor within the reactor apparatus (i.e.,via ducts, pipes or annular regions), and which has not been regeneratedor does not contain fresh catalyst, is not to be used in thedetermination of ACFE index.

[0080] In a preferred embodiment of this invention, a feed containing anoxygenate, and optionally a hydrocarbon, either separately or mixed withthe oxygenate, is contacted with a catalyst containing a SAPO molecularsieve at process conditions effective to produce olefins in a reactor.

[0081] Any standard reactor system can be used, including fixed bed,fluid bed or moving bed systems. Preferred reactors are co-current riserreactors and short contact time, countercurrent free-fall reactors.Desirably, the reactor is one in which an oxygenate feedstock can becontacted with a molecular sieve catalyst at a weight hourly spacevelocity (WHSV) of at least about 1 hr⁻¹, preferably in the range offrom about 1 hr⁻¹ to 1000 hr⁻¹, more preferably in the range of fromabout 20 hr⁻¹ to 1000 hr⁻¹, and most preferably in the range of fromabout 20 hr⁻¹ to 500 hr⁻¹. WHSV is defined herein as the weight ofoxygenate, and hydrocarbon which may optionally be in the feed, per hourper weight of the molecular sieve content of the catalyst. Because thecatalyst or the feedstock may contain other materials which act asinerts or diluents, the WHSV is calculated on the weight basis of theoxygenate feed, and any hydrocarbon which may be present, and themolecular sieve contained in the catalyst.

[0082] Preferably, the oxygenate feed is contacted with the catalystwhen the oxygenate is in a vapor phase. Alternately, the process may becarried out in a liquid or a mixed vapor/liquid phase. When the processis carried out in a liquid phase or a mixed vapor/liquid phase,different conversions and selectivities of feed-to-product may resultdepending upon the catalyst and reaction conditions.

[0083] The process can generally be carried out at a wide range oftemperatures. An effective operating temperature is at least about 200°C., preferably at least about 300° C., more preferably at least about350° C. and a temperature of at most about 700° C., preferably at mostabout 650° C., and more preferably at most about 600° C. At the lowerend of the temperature range, the formation of the desired olefinproducts may become markedly slow. At the upper end of the temperaturerange, the process may not form an optimum amount of product.

[0084] It is highly desirable to operate at a temperature of at least300° C. and a Temperature Corrected Normalized Methane Sensitivity(TCNMS) of less than about 0.016. It is particularly preferred that thereaction conditions for making olefin from oxygenate comprise a WHSV ofat least about 20 hr⁻¹ producing olefins and a TCNMS of less than about0.016.

[0085] As used herein, TCNMS is defined as the Normalized MethaneSelectivity (NMS) when the temperature is less than 400° C. The NMS isdefined as the methane product yield divided by the ethylene productyield wherein each yield is measured on, or is converted to, a weight %basis. When the temperature is 400° C. or greater, the TCNMS is definedby the following equation, in which T is the average temperature withinthe reactor in ° C.:${TCNMS} = \frac{NMS}{1 + \left( {\left( {\left( {T - 400} \right)/400} \right) \times 14.84} \right)}$

[0086] The pressure also may vary over a wide range, includingautogenous pressures. Effective pressures may be in, but are notnecessarily limited to, oxygenate partial pressures at least 1 psia (6.9kPa), preferably at least 5 psia (34.5 kPa). The process is particularlyeffective at higher oxygenate partial pressures, such as an oxygenatepartial pressure of greater than 20 psia (137.9 kPa). Preferably, theoxygenate partial pressure is at least about 25 psia (172.4 kPa), morepreferably at least about 30 psia (206.8 kPa). For practical designpurposes it is desirable to operate at a methanol partial pressure ofnot greater than about 500 psia (3447.4 kPa), preferably not greaterthan about 400 psia (2757.9 kPa), most preferably not greater than about300 psia (2068.4 kPa).

[0087] The conversion of oxygenates to produce light olefins may becarried out in a variety of catalytic reactors. Reactor types includefixed bed reactors, fluid bed reactors, and concurrent riser reactors asdescribed in “Free Fall Reactor”, Fluidization Engineering, D. Kunii andO. Levenspiel, Robert E. Krieger Publishing Co. NY, 1977, expresslyincorporated herein by reference. Additionally, countercurrent free fallreactors may be used in the conversion process as described in U.S. Pat.No. 4,068,136 and “Riser Reactor”, Fluidization and Fluid-ParticleSystems, pages 48-59, F. A. Zenz and D. F. Othmo, Reinhold PublishingCorp., NY 1960, the detailed descriptions of which are also expresslyincorporated herein by reference.

[0088] In a preferred embodiment of the continuous operation, only aportion of the catalyst is removed from the reactor and sent to theregenerator to remove the accumulated coke deposits that result duringthe catalytic reaction. In the regenerator, the catalyst is contactedwith a regeneration medium containing oxygen or other oxidants. Examplesof other oxidants include O₃, SO₃, N₂O, NO, NO₂, N₂O₅, and mixturesthereof. It is preferred to supply O₂ in the form of air. The air can bediluted with nitrogen, CO₂, or flue gas, and steam may be added.Desirably, the O₂ concentration in the regenerator is reduced to acontrolled level to minimize overheating or the creation of hot spots inthe spent or deactivated catalyst. The deactivated catalyst also may beregenerated reductively with H₂, CO, mixtures thereof, or other suitablereducing agents. A combination of oxidative regeneration and reductiveregeneration can also be employed.

[0089] In essence, the coke deposits are removed from the catalystduring the regeneration process, forming a regenerated catalyst. Theregenerated catalyst is then returned to the reactor for further contactwith feed. Typical regeneration temperatures are in the range of250-700° C., desirably in the range of 350-700° C. Preferably,regeneration is carried out at a temperature range of 450-700° C.

[0090] In one embodiment, the reactor and regenerator are configuredsuch that the feed contacts the regenerated catalyst before it isreturned to the reactor. In an alternative embodiment, the reactor andregenerator are configured such that the feed contacts the regeneratedcatalyst after it is returned to the reactor. In yet another embodiment,the feed stream can be split such that feed contacts regeneratedcatalyst before it is returned to the reactor and after it has beenreturned to the reactor. It is preferred that the catalyst within thereactor have an average level of coke effective for selectivity toethylene and/or propylene. Preferably, the average coke level on thecatalyst will be from about 2 wt. % to about 30 wt. %, more preferablyfrom about 2 wt. % to about 20 wt. %. In order to maintain this averagelevel of coke on catalyst, the entire volume of catalyst can bepartially regenerated under conditions effective to maintain the desiredcoke content on catalyst. It is preferred, however, to recycle only aportion of the coked catalyst for feed contact without regenerating.This recycle can be performed either internal or external to thereactor. The portion of coked catalyst to be regenerated is preferablyregenerated under conditions effective to obtain a regenerated catalysthaving a coke content of less than 2 wt. %, preferably less than 1.5 wt.%, and most preferably less than 1.0 wt. %.

[0091] In order to make up for any catalyst loss during the regenerationor reaction process, fresh catalyst can be added. Preferably, the freshcatalyst is added to the regenerated catalyst after it is removed fromthe regenerator, and then both are added to the reactor. However, thefresh catalyst can be added to the reactor independently of theregenerated catalyst. Any, amount of fresh catalyst can be added, but itis preferred that an ACFE index of at least 1.5 be maintained.

[0092] One skilled in the art will also appreciate that the olefinsproduced by the oxygenate-to-olefin conversion reaction of the presentinvention can be polymerized to form polyolefins, particularlypolyethylene and polypropylene. Processes for forming polyolefins fromolefins are known in the art. Catalytic processes are preferred.Particularly preferred are metallocene, Ziegler/Natta and acid catalyticsystems. See, for example, U.S. Pat. Nos. 3,258,455; 3,305,538;3,364,190; 5,892,079; 4,659,685; 4,076,698; 3,645,992; 4,302,565; and4,243,691, the catalyst and process descriptions of each being expresslyincorporated herein by reference. In general, these methods involvecontacting the olefin product with a polyolefin-forming catalyst at apressure and temperature effective to form the polyolefin product.

[0093] A preferred polyolefin-forming catalyst is a metallocenecatalyst. The preferred temperature range of operation is between 50 and240° C. and the reaction can be carried out at low, medium or highpressure, being anywhere within the range of about 1 to 200 bars. Forprocesses carried out in solution, an inert diluent can be used, and thepreferred operating pressure range is between 10 and 150 bars, with apreferred temperature range of between 120 and 230° C. For gas phaseprocesses, it is preferred that the temperature generally be within arange of 60 to 160° C., and that the operating pressure be between 5 and50 bars.

[0094] In addition to polyolefins, numerous other olefin derivatives maybe formed from the olefins recovered therefrom. These include, but arenot limited to, aldehydes, alcohols, acetic acid, linear alpha olefins,vinyl acetate, ethylene dichloride and vinyl chloride, ethylbenzene,ethylene oxide, cumene, isopropyl alcohol, acrolein, allyl chloride,propylene oxide, acrylic acid, ethylene-propylene rubbers, andacrylonitrile, and trimers and dimers of ethylene, propylene orbutylenes. The methods of manufacturing these derivatives are well knownin the art, and therefore, are not discussed herein.

[0095] This invention will be better understood with reference to thefollowing examples, which are intended to illustrate specificembodiments within the overall scope of the invention as claimed.

EXAMPLE 1 Calcination of SAPO-34 to Remove Template(s)

[0096] SAPO-34, is made by hydrothermal crystallization of a mixturecontaining water, a silica source, an alumina source, a phosphorussource, as well as tetraethylammonium hydroxide (TEAOH) and dipropylamine (DPA) as the templating agents, and is hereinafter referred to asSample X (uncalcined). Sample X is then calcined in air at 600° C. for 3hours to remove the template(s) and stored at 200° C. before use. Thesolid obtained after calcination is hereinafter referred to as Sample Y.

EXAMPLE 2 Dimethyl Zinc Treatment for SAPO-34

[0097] Under an N₂ atmosphere, 1.6 g of SAPO-34 (Sample Y) is suspendedin 50 ml of anhydrous heptane in a 100-ml round-bottom flask. Dimethylzinc, 0.90 ml of 1.0 M solution in heptane, is slowly added to themixture via a gas-tight syringe. The starting ratio of zinc to siliconin the SAPO-34 is 0.50. The mixture is stirred at room temperature for20 hr and centrifuged. The isolated solid is then stirred in 50 ml ofanhydrous methanol for 4 hr at room temperature, centrifuged, and driedat 105° C. for one day. The solid is calcined at 600° C. for 3 hr beforeuse and hereinafter referred to as Sample A.

EXAMPLE 3 Dimethyl Zinc Treatment for SAPO-34

[0098] Under an N₂ atmosphere, 2.8 g of SAPO-34 (Sample Y), is suspendedin 50 ml of anhydrous heptane in a 100-ml round-bottom flask. Dimethylzinc, 0.84 ml of 1.0 M solution in heptane, is slowly added to themixture via a gas-tight syringe. The starting ratio of zinc to siliconin the SAPO-34 is 0.25. The mixture is stirred at room temperature for20 hr and centrifuged. The isolated solid is then stirred in 50 ml ofanhydrous methanol for 4 hr at room temperature, centrifuged, and driedat 105° C. for one day. The solid is calcined at 600° C. for 3 hr beforeuse and hereinafter referred to as Sample B.

EXAMPLE 4 Dimethyl Zinc Treatment for SAP-34

[0099] Under an N₂ atmosphere, 2.2 g of SAPO-34 (Sample Y) is suspendedin 50 ml of anhydrous heptane in a 100-ml round-bottom flask. Dimethylzinc, 1.40 ml of 1.0 M solution in heptane, is slowly added to themixture via a gas-tight syringe. The starting ratio of zinc to siliconin the SAPO-34 is 0.60. The mixture is stirred at room temperature for20 hr and centrifuged. The isolated solid is then stirred in 50 ml ofanhydrous methanol for 4 hr at room temperature, centrifuged, and driedat 105° C. for one day. The solid is calcined at 600° C. for 3 hr beforeuse and hereinafter referred to as Sample C.

EXAMPLE 5 Dimethyl Zinc Treatment for SAPO-34

[0100] Under an N₂ atmosphere, 1.6 g of SAPO-34 (Sample Y) is suspendedin 50 ml of anhydrous heptane in a 100-ml round-bottom flask. Dimethylzinc, 3.50 ml of 1.0 M solution in heptane, is slowly added to themixture via a gas-tight syringe. The starting ratio of zinc to siliconin the SAPO-34 is 2.00. The mixture is stirred at room temperature for20 hr and centrifuged. The isolated solid is then stirred in 50 ml ofanhydrous methanol for 4 hr at room temperature, centrifuged, and driedat 105° C. for one day. The solid is calcined at 600° C. for 3 hr beforeuse and hereinafter referred to as Sample D.

EXAMPLE 6 Dimethyl Zinc Treatment for SAPO-34

[0101] Under an N₂ atmosphere, 4.2 g of SAPO-34 (Sample Y) is suspendedin 150 ml of anhydrous heptane in a 500-ml round-bottom flask. Dimethylzinc, 50.00 ml of 1.0 M solution in heptane, is slowly added to themixture via a gas-tight syringe. The starting ratio of zinc to siliconin the SAPO-34 is 9.00. The mixture is stirred at room temperature for20 hr and centrifuged. The isolated solid is then stirred in 50 ml ofanhydrous methanol for 4 hr at room temperature, centrifuged, and driedat 105° C. for one day. The solid is calcined at 600° C. for 3 hr beforeuse and hereinafter referred to as Sample E.

COMPARATIVE EXAMPLE 7 Framework Incorporated Zinc SAPO-34

[0102] Framework incorporated zinc SAPO-34 is prepared hydrothermally byadding zinc acetate to the synthesis gel of SAPO-34 where triethylamine(TEA) is used as the template, following the procedures reported in EP1143833 A1, which is fully incorporated herein by reference. The solidis hereinafter referred to as Sample F.

COMPARATIVE EXAMPLE 8 Cation Exchange with SAPO-34

[0103] 3.3 g of SAPO-34 (Sample X) is refluxed with 0.86 g ofZn(NO₃)₂.6H₂O in 35 ml of distilled water for 4 hr. The mixture isfiltered and dried at 105° C. overnight. The solid is hereinafterreferred to as Sample G.

COMPARATIVE EXAMPLE 9 Cation Exchange with SAPO-34

[0104] 4.0 g of calcined SAPO-34 (Sample Y) is refluxed with 1.00 g ofZn(NO₃)₂.6H₂O in 50 ml of distilled water for 4 hr. The mixture isfiltered and dried at 105° C. overnight. The solid is hereinafterreferred to as Sample H.

COMPARATIVE EXAMPLE 10 SAPO-34 Impregnation Via Incipient Wetness

[0105] 4.0 g of SAPO-34 (Sample X) is slowly wetted with a solution of0.22 g of Zn(NO₃)₂.6H₂O dissolved in 2.0 ml of de-ionized water. The wetmixture is dried at 105° C. overnight. The solid is hereinafter referredto as Sample I.

COMPARATIVE EXAMPLE 11 SAPO-34 Impregnation Via Incipient Wetness

[0106] 4.0 g of SAPO-34 (Sample X), is slowly wetted with a solution of0.52 g of Zn(NO₃)₂.6H₂O dissolved in 2.0 ml of de-ionized water. The wetmixture is dried at 105° C. overnight. The solid is hereinafter referredto as Sample J.

EXAMPLE 12 Methylmagnesium Bromide Treatment of SAPO-34

[0107] Under an N₂ atmosphere, 7.0 g of SAPO-34 (Sample Y) is placed ina 250-ml schlenk flask and chilled with an ice/acetone bath. A volume of100 ml methylmagnesium bromide solution (0.7 M in 3/1toluene/tetrahydrofuran (THF)) is cannulated into the flask. The mixtureis allowed to warm up to room temperature and stirred at roomtemperature for 21 hr. The mixture is then filtered under N₂, washedwith pentane, followed by ether, and dried under vacuum for 4 hr. Thedry powder is stirred with 50 ml of anhydrous methanol for 4 hr andcentrifuged. The solid is dried under vacuum overnight and calcined at600° C. for 3 hr before use and hereinafter referred to as Sample K.

EXAMPLE 13 Dimethyl Zinc Treatment for SAPO-34

[0108] Under an N₂ atmosphere, 23.2 g of SAPO-34 (Sample Y) is suspendedin 200 ml of anhydrous heptane in a 500-ml round-bottom flask. Dimethylzinc, 7.0 ml of 1.0 M solution in heptane, is slowly added to themixture via a gas-tight syringe. The starting ratio of zinc to siliconin the SAPO-34 is 0.25. The mixture is stirred at room temperature for20 hr and centrifuged. The isolated solid is dried at 105° C. for oneday and hereinafter referred to as Sample L.

EXAMPLE 14 Repetitive Low Dose Dimethyl Zinc Treatment for SAPO-34

[0109] Under an N₂ atmosphere, 15.4 g of Sample L is suspended in 150 mlof anhydrous heptane in a 500-ml round-bottom flask. Dimethyl zinc, 5.0ml of 1.0 M solution in heptane, is slowly added to the mixture via agas-tight syringe to bring the total starting ratio of zinc tosilicon-in the SAPO-34 to 0.5. The mixture is stirred at roomtemperature for 20 hr and centrifuged. The isolated solid is dried at105° C. for one day and hereinafter referred to as Sample M.

EXAMPLE 15 Repetitive Low Dose Dimethyl Zinc Treatment for SAPO-34

[0110] Under an N₂ atmosphere, 9.7 g of Sample M is suspended in 100 mlof anhydrous heptane in a 250-ml round-bottom flask. Dimethyl zinc, 3.5ml of 1.0 M solution in heptane, is slowly added to the mixture via agas-tight syringe to bring the total starting ratio of zinc to siliconin the SAPO-34 to 0.75. The mixture is stirred at room temperature for20 hr and centrifuged. The isolated solid is dried at 105° C. for oneday and hereinafter referred to as Sample N.

EXAMPLE 16 Repetitive Low Dose Dimethyl Zinc Treatment for SAPO-34

[0111] Under an N₂ atmosphere, 5.2 g of Sample N is suspended in 60 mlof anhydrous heptane in a 250-ml round-bottom flask. Dimethyl zinc, 2.0ml of 1.0 M solution in heptane, is slowly added to the mixture via agas-tight syringe to bring the total starting ratio of zinc to siliconin the SAPO-34 to 1.0. The mixture is stirred at room temperature for 20hr and centrifuged. The isolated solid is dried at 105° C. for one dayand hereinafter referred to as Sample O.

EXAMPLE 17 Methane Formation During Dimethyl Zinc Treatment of SAPO-34

[0112] Under an N₂ atmosphere, 1.2 g of Sample Y is placed in a 50-mlround bottom flask and is evacuated under vacuum. Anhydrous heptane (24ml) is added. The mixture is stirred under N₂, and 1.6 ml of dimethylzinc solution (1.0 M in heptane) is added via a gas-tight syringe. Thelevel of methane in the head space of the flask is analyzed by gaschromatography (GC) in order to follow the reaction.

[0113]FIG. 1 shows the evolution of methane with time after dimethylzinc is added to SAPO-34. The Y-axis is the GC peak area ratio ofmethane vs. the solvent heptane (A_(CH) ₄ /A_(C) ₇ _(H) ₁₆ ). It isbelieved that if dimethyl zinc reacts mostly with the exterior acidsites of SAPO-34 and inadvertent moisture, immediate release of methanewill result and the level of methane will rapidly reach its maximum. Asshown in FIG. 1, it takes more than three hours for methane to reach itsmaximum level, indicating that dimethyl zinc diffuses inside the cage ofSAPO-34 and reacts mostly with the interior acid sites.

[0114] The reaction is stopped and the solid isolated afterA_(CH4)/A_(C) ₇ _(H) ₁₆ has reached its maximum. The Zn/Si atomic ratioin the isolated solid is 0.73 as determined by elemental analysis (seeExample 19 below).

EXAMPLE 18 Methane Formation During Methylmagnesium Bromide Treatment ofSAPO-34

[0115] Under an N₂ atmosphere, 1.2 g of Sample Y is suspended in 30 mlof a 3/1 mixture of anhydrous toluene/anhydrous tetrahydrofuran in a50-ml round bottom flask. A volume of 1.4 ml of methylmagnesium bromidesolution (1.4 M in 3/1 toluene/THF) is added to the mixture via a gastight syringe. The level of methane in the head space of the flask isanalyzed by gas chromatography (GC) in order to follow the reaction.

[0116]FIG. 2 shows the evolution of methane with time aftermethylmagnesium bromide is added to SAPO-34. The Y-axis is the GC peakarea ratio of methane vs. the solvent tetrahydrofuran (A_(CH) ₄/A_(THF)). It is believed that if methylmagnesium bromide reacts mostlywith the exterior acid sites of SAPO-34 and inadvertent moisture,immediate release of methane will result and the level of methane willrapidly reach its maximum. As shown in FIG. 2, it takes about two hoursfor methane level to reach its maximum, indicating that methylmagnesiumbromide diffuses inside the cage of SAPO-34 and reacts with the interioracid sites.

[0117] The reaction is stopped and the solid isolated after A_(CH) ₄/A_(THF) has reached its maximum. The Mg/Si atomic ratio in the isolatedsolid is 0.43 as determined by elemental analysis (see Example 19below).

EXAMPLE 19 Elemental Compositions of Modified SAPO-34

[0118] Elemental compositions of modified SAPO-34 samples are analyzedby Inductively Coupled Plasma/Atomic Emission Spectroscopy (ICP/AES) andthe results are listed below in Table 1 (Samples A-J). Clearly, theamount of zinc incorporated in SAPO-34 can be controlled by varying thereaction stoichiometry between dimethyl zinc and SAPO-34 in Samples A-E.Similarly, the amount of zinc can also be controlled in the impregnatedSamples I and J by varying the amount of zinc nitrate used. In contrast,the amount of zinc incorporated is limited in the cation-exchangedSamples G and H.

EXAMPLE 20 Methanol Uptake of Modified SAPO-34

[0119] Methanol uptake (expressed as weight percentage of methanoladsorbed by the molecular sieve) is measured gravimetrically and theresults are listed below in Table 2. Clearly, samples of SAPO-34modified with dimethyl zinc or methylmagnesium bromide have reducedmethanol uptake, consistent with reduced cage volume after modification.

EXAMPLE 21 MAS ¹H NMR Measurement of Modified SAPO-34

[0120] The Brønsted acid site density of the modified materials ismeasured by Magic Angle Spinning proton NMR spectroscopy (MAS ¹H NMR).The ¹H MAS NMR spectra are obtained on a Bruker AMX360 (360.13 MHz for¹H) wide bore spectrometer with a 4-mm (o.d.) MAS probe using 10-kHzspinning, 3.0 ms 90° pulses, a 30 s pulse delay, and 32 scans werecollected. The absolute amount of ¹H in each sample is determined bydirectly comparing the experimental spectral area relative to that of anexternal quantification standard and weight normalized. The externalstandards and the samples are run back-to-back under identicalconditions to minimize any effects due to the spectrometer instability.The external quantification standard used isoctakis(trimethylsiloxy)silesquioxane, more commonly known as Q8M8. Q8M8is a solid at room temperature, has similar tuning characteristics tosilicoaluminophosphates, and has a single peak at about 0.3 ppm fromtetramethylsilane (TMS). It is commercially available from StremChemicals (CAS No. 51777-38-9). Measurements done in quadruplicate onsimilar systems give a standard deviation of <4% for this methodology.The results for Samples L-O as well as those for comparative Samples Fand H are shown in FIG. 3.

[0121]FIG. 3 shows that: 1) the Brønsted acid site (3.7 ppm) densitydecreases proportionally with increasing amount of zinc incorporation, aresult of increasing degree of dimethyl zinc modification; and 2) a newpeak (1.0 ppm) appears in the dimethyl zinc modified samples, whichgrows proportionally with increasing amount of zinc incorporation. Thedata are summarized below in Table 3.

[0122] In contrast, the peak around 1 ppm is not seen in either Sample F(framework incorporated zinc SAPO-34) or Sample H (Zn²⁺ cation exchangedSAPO-34). Therefore MAS ¹H NMR clearly shows the structural differencebetween dimethyl zinc modified SAPO-34 and other zinc-containing SAPO-34wherein zinc is introduced via other methods.

EXAMPLE 22 Conversion of Methanol to Olefins (MTO)

[0123] Conversion of methanol to olefins is carried out in a continuous,tubular, stainless steel reactor (i.d.=0.4 cm; l=13 cm). An amount of0.025-0.05 g of the calcined and pelletized (40-80 mesh) catalyst isloaded along with quartz granules in the center zone of the tube. Thecatalyst is heated to 450° C. in flowing-nitrogen prior to the MTOreaction. The reaction temperature is either 400° C. or 450° C. asindicated in the Tables below. In all MTO runs, the pressure of thereactor is maintained at 15 psig with the use of a back-pressureregulator. Methanol is fed to the reactor as saturated vapor by bubblingnitrogen through a reservoir of methanol held at 20° C. The effluentfrom the reactor is analyzed with an HP5890 Series II Plus GasChromatograph with a flame ionization detector (FID). In order tocompare selectivity of different catalysts, the weight hourly spacevelocity (WHSV) is adjusted to keep conversion level similar (90-95%).Selectivity is chosen at the conversion level shown. Catalyst lifetimeis defined as the amount of methanol fed through the catalyst from thebeginning of reaction to the point where about 50% oxygenates areconverted. The results are shown below in Tables 4-6.

[0124] Shown in Table 4 below are the MTO product selectivity (400° C.)for Samples A, D and K modified according to the method of the presentinvention. Results for Sample Y are also shown for comparison.

[0125] Table 5 below shows MTO product selectivity (450° C.) for SamplesB and C modified according to the present invention and comparativeSamples F (framework incorporated) and G (cation exchange withtemplate). Results for Sample Y are also shown for comparison.

[0126] MTO product selectivity (450° C.) is shown in Table 6 below forcomparative Samples H (cation exchange without template), I(impregnation) and J (impregnation). Results for Sample Y are also shownfor comparison.

EXAMPLE 23 Conversion of Methanol to Olefins (MTO) at High Pressure

[0127] Samples of dimethyl zinc modified SAPO-34 (Sample L-O) have alsobeen tested for MTO reactions in a high-pressure micro-reactor. Typicalconditions are: 25 psig, 475° C., and WHSV=100 h⁻¹. The results arelisted in Table 7 below. Selectivity shown is the integrated selectivitythrough the course of the reaction. Catalyst lifetime is defined as thetotal amount of methanol converted per gram of catalyst from beginningof reaction to a conversion level of about 10%.

[0128] The MTO performance results clearly indicate that theorganometallic modification results in an increase in selectivity towardethylene (Samples A-D, L-O). Total ethylene and propylene selectivityalso increases with organometallic treatment (Samples A-D).

[0129] Framework incorporated ZnSAPO-34 (Sample F) with similar amountof zinc does not show significant advantage in terms of olefinselectivity. In addition, it is far more difficult to regenerateframework zinc than to replace intra-/inter-cage zinc using dimethylzinc. Cation exchanged SAPO-34 (Samples G and H) that starts with eithercalcined (without template) or uncalcined (with template) SAPO-34 doesnot show significant increase in ethylene selectivity either.Impregnation methods such as incipient wetness (Samples I and J) canachieve similar level of zinc to those of dimethyl zinc modification,however the selectivity toward ethylene does not increase assignificantly compared to those of the organometallic modificationaccording to the method of the present invention.

EXAMPLE 24 Conversion of Methanol to Olefins (MTO) for RegeneratedCatalysts

[0130] Deactivated catalyst (Sample B) after methanol-to-olefinsconversion according to Example 22 above is regenerated in-situ bypassing air through the reactor at 550° C. for two hours. MTO conversionis then resumed under identical conditions used for the fresh catalyst.The results are shown in FIG. 4. Little or no change in performance isobserved, indicating good hydrothermal stability for dimethyl zincmodified SAPO-34 (Sample B). TABLE 1 Elemental composition of modifiedSAPO-34 Metal Metal (M) loading Composition (atomic ratio) Sampleincorporated (wt. %) M Si Al P M/Si Y None 0.0 0 0.142 1 0.768 0 A Zn2.6 0.049 0.14 1 0.776 0.35 B Zn 1.5 0.028 0.138 1 0.745 0.21 C Zn 3.50.066 0.141 1 0.757 0.47 D Zn 9.6 0.2 0.143 1 0.755 1.4 E Zn 18.7 0.440.135 1 0.72 3.3 F Zn 2.5 0.05 0.106 1 1.02 0.47 G Zn 0.3 0.006 0.134 10.748 0.04 H Zn 0.28 0.0052 0.138 1 0.751 0.04 I Zn 1.2 0.022 0.143 10.767 0.15 J Zn 3.5 0.067 0.143 1 0.763 0.47 K Mg 1.9 0.094 0.138 10.748 0.68

[0131] TABLE 2 Methanol uptake of modified SAPO-34 Sample Metal (M)incorporated Methanol uptake (wt %) Y None 25 A Zn 22 D Zn 15 E Zn 6 GZn 20 K Mg 22

[0132] TABLE 3 MAS ¹H NMR of dimethyl zinc modified SAPO-34 New peakBrφnsted acid site (1.0 ppm) Composition Zn loading (3.7 ppm) densitydensity Sample Zn Si Al P Zn/Si (wt. %) (mmole/g) (mmole/g) Y 0 0.142 10.768 0 0.0 1.37 0 L 0.03 0.149 1 0.789 0.20 1.6 1.08 0.18 M 0.062 0.1491 0.781 0.42 3.2 0.88 0.26 N 0.096 0.156 1 0.794 0.61 4.9 0.74 0.35 O0.152 0.174 1 0.779 0.87 7.4 0.54 0.28

[0133] TABLE 4 MTO performance (400° C.) for ZnMe₂ and MeMgBr modifiedSAPO-34 Sample Y A D K M/Si ratio 0 0.35 1.4 0.68 Modification NoneZnMe₂ ZnMe₂ MeMgBr WHSV (h⁻¹) 20 15 2.5 10 Conversion (%) 97 94.2 92 95Lifetime 16 11 1.3 11.5 (g MeOH fed/g catalyst) Selectivity C₂ ⁼ 33.337.3 49.4 32.4 (wt %) C₃ ⁼ 44.9 41.8 33.5 45.4 C₄ ⁼ 13.9 10.2 7 13.3 CH₄0.55 1.67 3.9 0.77 C₂ 0.82 0.97 0.26 1.39 C₃ 1.62 1.69 0.97 1.82 C₄ 0.590.48 0.23 0.87 C₅-C₆ 4.6 5.92 4.8 4.5 C₂ ⁼ /C₃ ⁼ 0.75 0.9 1.5 0.71 C₂⁼ + C₃ ⁼ 78.2 79.1 82.9 77.8

[0134] TABLE 5 MTO performance (450° C.) for SAPO-34 modified with zincaccording to different methods. Sample Y B C F G Zn/Si ratio 0 0.2 0.470.5 0.045 Modification None ZnMe₂ ZnMe₂ Framework Cation incorporatedexchange WHSV (h⁻¹) 20 30 15 25 30 Conversion (%) 90 92 95 91 90Lifetime 19 7 5 8 18 (g MeOH fed/g catalyst) Selectivity C₂ ⁼ 38.5 44.552 38.9 41.9 (wt %) C₃ ⁼ 38.3 37.2 29.2 38.2 37.2 C₄ ⁼ 11.5 8.3 7.2 11.810.1 CH₄ 1.1 3 7.4 4 2.2 C₂ 0.9 1.1 0.5 0.9 0.3 C₃ 0.8 1.0 0.5 1.2 0.7C₄ 0.2 0.2 0.05 0.2 0.2 C₅-C₆ 8.6 4.6 3.1 4.8 7.2 C₂ ⁼ /C₃ ⁼ 1 1.2 1.8 11.1 C₂ ⁼ + C₃ ⁼(wt %) 76.8 81.7 81.2 77.1 79.2

[0135] TABLE 6 MTO performance (450° C.) for SAPO-34 modified with zincaccording to different methods. Sample Y H I J Zn/Si ratio 0 0.038 0.150.47 Modification None Cation Impregnation Impregnation exchange (w/otemplate) WHSV (h⁻¹) 30 60 30 30 Conversion (%) 95 96 95 94 Lifetime 2512 14 7 (g MeOH fed/g catalyst) Selectivity C₂ ⁼ 41 35.67 45.6 48.6 (wt%) C₃ ⁼ 36.9 41.81 36.1 34.6 C₄ ⁼ 10.8 12.1 9.4 8.1 CH₄ 2.2 3.36 1.8 3.4C₂ 0.3 0.31 0.4 0.35 C₃ 0.75 1.05 0.6 0.45 C₄ 0.14 0.14 0.12 0.1 C₅-C₆7.8 5.2 6 4.4 C₂ ⁼ /C₃ ⁼ 1.1 0.85 1.26 1.4 C₂ ⁼ + C₃ ⁼ 77.9 77.5 81.783.2

[0136] TABLE 7 MTO performance (25 psig, 475° C.) for SAPO-34 modifiedwith zinc according to the present invention. Sample Y L M N O Zn/Siratio 0 0.20 0.42 0.61 0.87 Modification None ZnMe₂ ZnMe₂ ZnMe₂ ZnMe₂WHSV (h⁻¹) 100 100 100 100 100 Lifetime 14.3 14.6 6.34 2.4 2.1 (g MeOHconverted/g catalyst) Selectivity C₂ ⁼ 35.8 37.6 36.87 34.04 32.84 (wt%) C₃ ⁼ 40.8 38.1 37.35 33.04 33.33 C₄ ⁼ 14.8 13.8 12.25 9.47 9.67 CH₄1.44 2.14 3.05 5.61 5.89 C₂ 0.71 0.73 0.91 1.9 1.84 C₃ 1.85 1.64 2.03.92 3.75 C₄ 0.0 0.02 0.15 0.49 0.42 C₅-C₆ 1.97 2.56 2.77 2.73 3.34 C₂ ⁼/C₃ ⁼ 0.88 0.99 0.99 1.03 0.99 C₂ ⁼ + C₃ ⁼(wt %) 76.63 75.65 74.22 67.0866.16

[0137] Having now fully described this invention, it will be appreciatedby those skilled in the art that the invention can be performed within awide range of parameters within what is claimed, without departing fromthe spirit and scope of the invention.

1-59. (Cancelled)
 60. A method of making an olefin product comprisingcontacting a feedstock comprising at least one organic compound thatcontains at least one oxygen atom (oxygenate) in the presence of acatalyst comprising a calcined, organometallic treated molecular sieveunder conditions suitable to convert the oxygenate into olefins; whereinsaid calcined, organometallic treated molecular sieve is prepared by aprocess comprising: a) providing a molecular sieve having at least onehydroxyl group; b) contacting said molecular sieve with a solutioncomprising an organometallic compound and a non-proton donating solvent,wherein said organometallic compound comprises at least one metal boundto at least one alkyl group; and, c) separating the organometallictreated molecular sieve from said solution.
 61. The method of claim 60,wherein the oxygenate is selected from the group consisting of methanol,ethanol, dimethyl ether, methylethyl ether, diethyl ether, dimethylcarbonate, methyl formate, and mixtures thereof.
 62. The method of claim60, wherein the oxygenate is methanol.
 63. The method of claim 62,wherein the olefin product has an ethylene to propylene ratio of atleast about 0.90.
 64. The method of claim 63, wherein the olefin producthas an ethylene to propylene ratio of at least about 0.95.
 65. Themethod of claim 64, wherein the olefin product has an ethylene topropylene ratio of at least about 0.98.
 66. The method of claim 60,wherein said catalyst further comprises a binder.
 67. The method ofclaim 66, wherein said molecular sieve is a silicoaluminophosphatemolecular sieve.
 68. The method of claim 67, wherein thesilicoaluminophosphate molecular sieve is selected from the groupconsisting of SAPO-17, SAPO-18, SAPO-34, SAPO-35, SAPO-44, SAPO-47,SAPO-56 and mixtures thereof.
 69. The method of claim 68, wherein thesilicoaluminophosphate molecular sieve is selected from the groupconsisting of SAPO-18, SAPO-34, intergrowths of SAPO-18 and SAPO-34 andmixtures thereof.
 70. The method of claim 69, wherein thesilicoaluminophosphate molecular sieve is SAPO-34.
 71. The method ofclaim 60, wherein the preparation of said calcined, organometallictreated molecular sieve further comprises calcining the molecular sieveprior to step b).
 72. The method of claim 71, wherein said calcining iscarried out at a temperature of at least about 550° C. and at most about700° C.
 73. The method of claim 71, wherein said calcining is carriedout in the presence of oxygen.
 74. The method of claim 71, wherein saidcalcining is carried out for a period of at least about 3 hours and atmost about 10 hours.
 75. The method of claim 60, wherein the preparationof said organometallic molecular sieve further comprises calcining theorganometallic treated molecular sieve after step b).
 76. The method ofclaim 75, wherein said calcining is carried out at a temperature of atleast about 550° C. and at most about 700° C.
 77. The method of claim75, wherein said calcining is carried out in the presence of oxygen. 78.The method of claim 75, wherein said calcining is carried out for aperiod of at least about 3 hours and at most about 10 hours.
 79. Themethod of claim 60, further comprising calcining both the molecularsieve prior to step b) and the organometallic treated molecular sieveafter step b).
 80. The method of claim 60, wherein step b) is carriedout with stirring.
 81. The method of claim 60, wherein the metal isselected from the group consisting of zinc, lithium, magnesium, gallium,germanium, and mixtures thereof.
 82. The method of claim 60, whereinsaid organometallic compound is selected from the group consisting ofmethyl lithium, butyl lithium, dimethyl zinc, diethyl zinc,ethylmagnesium bromide, methylmagnesium bromide, trimethyl gallium,triethyl gallium, tetraethyl gallium, tetramethylgallium, and mixturesthereof.
 83. The method of claim 60, wherein said organometalliccompound is dimethyl zinc.
 84. The method of claim 60, wherein saidorganometallic compound is methylmagnesium bromide.
 85. The method ofclaim 60, wherein said at least one alkyl group has from 1 to 6 carbonatoms.
 86. The method of claim 85, wherein said at least one alkyl groupis linear.
 87. The method of claim 60, wherein said non-proton donatingsolvent is selected from the group consisting of heptane,tetrahydrofuran, benzene, toluene, xylenes, diethyl ether and mixturesthereof.
 88. The method of claim 60, wherein the amount of metal loadingin the organometallic treated molecular sieve is at least about 0.05% bywt. metal and at most about 20 % by wt. metal.